Conventional electrophotographic photoreceptors include those which are close to a simple photoconductor, so-called Carlson's photoreceptors, those having an amorphous Se photosensitive layer, those having an amorphous Si layer, and ZnO-resin photoconductors which are similar to an amorphous Se layer. A photosensitive layer of separate function type using an organic semi-conductor has recently been put to practical use. Any of these electrophotographic techniques has been developed based on the conception of an analogue recording system in which a photoconductive material passing a photoelectric current in proportion to the amount of incident light is employed.
Electrophotographic techniques and computer communication techniques have recently been combined, and a printer or facsimile system has rapidly been introduced into an electrophotographic recording system. Accordingly, it has been demanded to displace the conventional analogue recording system for plain paper copiers (PPC) with a digital recording system in the field of electrophotography. For example, JP-A-1-169454 (corresponding to U.S. Pat. No. 4,963,452) (the term "JP-A" as used herein means an "unexamined published Japanese patent application") discloses the concept of a photoreceptor for digital light input. However, the publication affords no specific description about the materials of the photoreceptor for digital light input.